How did wealthier individuals in Pride and Prejudice have more choices than the poorer ones?

Although people were limited to a large extent by what
were considered the appropriate behaviours, occupations, and partners for men and women
of their class, the more money a person had, the more that person was free to act.
William Paley was rumoured to have excused his not signing the Feathers Tavern Petition
with the comment that a man with 8 children could not afford a conscience. In Austen, a
common obstacle to marriage choice is money. Darcy and Bentley, being rich, can afford
to marry beneath their social and economic station. Willoughby must seek his fortune
through marriage and cannot really afford to marry a Bennett. Charlotte Lucas must marry
the odius Mr. Collins to avoid being a burden to her family. Many of Austen's plots
hinge on the economic constraints on marriage.